Week 13 - Friday

 What did we talk about last time?  Server communications on a socket  Function pointers

There are only two kinds of programming languages: those people always bitch about and those nobody uses. Bjarne Stroustrup Inventor of C++ There are only two kinds of programming languages: those people always bitch about and those nobody uses. Bjarne Stroustrup Inventor of C++

 C++ is based on C and easier to use  You can declare variables anywhere ▪ Not the case in the C89 standard (where all variables had to be declared right after a block starts), but our gcc is following the C99 standard  It has function overloading  Most people think the I/O is cleaner  The big addition is OOP through classes  It's an approximate superset of C that includes most C structures

 gcc used to stand for the GNU C Compiler  When it became a suite of tools used for things other than C, they changed the name to the GNU Compiler Collection  The compiler for C++ is called g++ and is part of gcc, but it may need to be installed separately and doesn't come on all Linux installations by default  C++ files have the extensions.cc,.cpp,.cxx,.c++, and.C  I prefer.cpp, but.cc is also common g++ thing.cpp –o program

 C has too many ways to do things, but C++ is an order of magnitude worse  Syntax is a big mess of overlapping, ambiguous ideas  Which only got worse in the C++11 standard, which we aren't talking about  C++ tried to be reverse compatible with C, but not strictly true  It tried to be object-oriented, but not strictly true  The Standard Template Libraries are hideous compared to the Java Collection Framework  At the time, it was the best choice available for OOP, and now we're stuck with it

 It's not too different from C  We need different headers for C++ I/O #include using namespace std; int main() { cout << "Hello, world!" << endl; return 0; } #include using namespace std; int main() { cout << "Hello, world!" << endl; return 0; }

 Output uses the cout object (of type ostream )  Instead of using formatting strings, cout uses the idea of a stream, where objects are placed into the stream separated by the extraction operator <<  The endl object adds a newline to the stream  Of course, "\n" works too int x = 50; cout << "There are " << x << " ways to leave your lover." << endl; int x = 50; cout << "There are " << x << " ways to leave your lover." << endl;

 Basic output is easier  What about setting the width or precision?  You need to include the iomanip header  Put setw( width ) in the stream to make the items take up the specified width  Put setprecision ( precision ) in the stream to show a certain number of decimal places  Put fixed to force it to pad with zeroes when there isn't enough precision double dollars = 2.0; cout << "Give me $" << setw(10) << fixed << setprecision(2) << dollars << setw(0) << "!" << endl; //printf equivalent printf("Give me $%10.2f!\n", dollars); double dollars = 2.0; cout << "Give me $" << setw(10) << fixed << setprecision(2) << dollars << setw(0) << "!" << endl; //printf equivalent printf("Give me $%10.2f!\n", dollars);

 Input uses the cin object (of type istream )  cin also uses the idea of a stream, where items are read from the stream and separated by the insertion operator >>  It reads items using whitespace as the separator, just like scanf() int x = 0; int y = 0; int z = 0; cout << "Enter the x, y, and z values: "; cin >> x >> y >> z; int x = 0; int y = 0; int z = 0; cout << "Enter the x, y, and z values: "; cin >> x >> y >> z;

 Like Java, C++ has a class for holding strings, which makes life much easier  It's called string (with a lower case 's' )  You must include to use it  Unlike String in Java, string is mutable  You can use array-style indexing to get and set individual characters string a = "Can I kick it?"; string b = "Yes, you can!"; string c = a + " " + b; c[0] = 'D'; c[1] = 'i'; c[2] = 'd'; cout << c << endl; //prints Did I kick it? Yes, you can! string a = "Can I kick it?"; string b = "Yes, you can!"; string c = a + " " + b; c[0] = 'D'; c[1] = 'i'; c[2] = 'd'; cout << c << endl; //prints Did I kick it? Yes, you can!

 Java uses packages to keep different classes with the same name straight  C++ uses namespaces  The standard library includes I/O ( ), the string class ( ), STL containers (,,, and others)  If you use these in your program, put the following after your includes  The alternative is to specify the namespace by putting the it followed by two colons before the class name using namespace std; std::string name = "Ghostface Killah";

 Regular C++ functions are very similar to functions in C  A big difference is that prototypes are no longer optional if you want to call the function before it's defined  Unlike C, function overloading allowed: int max(int a, int b) { return a > b ? a : b; } int max(int a, int b, int c) { return max( a, max( b, c)); } int max(int a, int b) { return a > b ? a : b; } int max(int a, int b, int c) { return max( a, max( b, c)); }

 In C, all functions are pass by value  If you want to change an argument, you have to pass a pointer to the value  In C++, you can specify that a parameter is pass by reference  Changes to it are seen on the outside  You do this by putting an ampersand ( & ) before the variable name in the header void swap(int &a, int &b) { int temp = a; a = b; b = temp; } void swap(int &a, int &b) { int temp = a; a = b; b = temp; }

 Pass by reference is a great tool  You don't have to pass nearly as many pointers  If you want to change a pointer, you can pass it by reference instead of passing a pointer to a pointer  It does allow more mistakes  Leave off the ampersand and your function does nothing  Change things you didn't intend to change  You cannot pass a literal by reference swap(3, 9); //doesn't compile

 C++ also allows you to specify default values for function parameters  If you call a function and leave off those parameters, the default values will be used  Default parameters are only allowed for the rightmost grouping of parameters void build(int width = 2, int height = 4) { cout << "We built this house with " << width << " by " << height << "s."; } void build(int width = 2, int height = 4) { cout << "We built this house with " << width << " by " << height << "s."; } build(); //We built this house with 2 by 4s. build(3); //We built this house with 3 by 4s. build(6, 8); //We built this house with 6 by 8s. build(); //We built this house with 2 by 4s. build(3); //We built this house with 3 by 4s. build(6, 8); //We built this house with 6 by 8s.

 More C++

 Keep working on Project 6